The long term goals of this project are to understand the bases of the interactions between Schwann cells and axons. These include the mechanism of recognition, adhesion and in particular, the process of differentiation with respect to the synthesis of basal lamina and myelin. The immediate aims in the present proposal are to focus on the early molecular events during differentiation of the Schwann cell. Specific Aims 1 and 2 are designed to examine transcriptional and translational control of specific myelin proteins P0 and P2. It is known that addition of bovine axolemma to rat Schwann cells in culture results in increased expression of P0 protein. How this expression is regulated (increased transcription, stabilization of P0-mRNA, or translational or post-translational control) will be addressed, as well as the possible role of post-translational modification of the oligosaccharide portion of the protein in targeting of P0 to its destination in Schwann cells. Similar questions will be addressed to myelin P2 protein; although not glycosylated, P2 protein is probably involved in lipid transport and therefore information about the early events in its expression may shed light on its role in myelination. Both P0 and P2 will be studied by immunofluorescence, biochemical and molecular biological techniques. These studies are made possible by our ability to obtain and maintain large quantities of Schwann cells in culture by transfection of isolated Schwann cells with the SV40 large T antigen gene under the control of a metallothionein promoter. Specific Aim 3 is designed to improve the regulation of expression of the T antigen by use of synthetic metallothionein promoters, and to determine whether large T antigen affects the expression of myelin-specific components. In the latter instance, the effect of large T antigen on the expression of myelin protein may have a direct bearing on a human demyelinating disease, progressive multifocal leucoencephalopathy, a disease caused by JC virus. Moreover, the overall understanding of the interaction between axons and Schwann cells should provide insight into the pathophysiology of demyelination as well as repair by remyelination. This could result in a more rational approach to the treatment of human peripheral nerve diseases.